Refractory metallic body of high density and process for making the same



March 31. 1925. 1,531,666

- c. A. LAISE REFRACTORY METALLIC BODY OF HIGH DENSITY AND PROCESS FORMAKING THE SAME Filed June 12, 1922 :rrgi.

2 L r INVENTOR.

2 2'7 16 a Cleans HLcuse W AD -M '76 Z4. ATTORNEYC Patented To all whomit may o. r s A. miss; or Awxmz; new mam. cromr mmfanirc Bony or mennmesrrr am) PM. son.

Be it known that I, CLEMENS A. lia se, a citizen of the United States,and a resident of Wee'hawkemfcounty of Hudson, State of New Jerseyrha've invented certain new and useful Improvements in RefractoryMetallic Bodies of High Density and Processes for Making the Same, of.which thefioll'owing is a specification. m i

his invention relates to the production ofmetallic bodies of refractorymetals of a density or specific gravity above 18, such bodiesbeingof'small dimensions usually not exceeding 5- to 10 grams in weight. V

I have discovered that instea of mechanically working metallic bars ofrefractory metals by hammering, swaging, rolling or drawing the saidmetals and then shaping them into small bodies by cutting or punching, Ican press up the refractory metallic powders into any desired sha pe,then fuse or sinter the pressed up bodies into solid ordinarily desiredfor use I which the products are to use of specific gravity ofapproximately 18 and sirable to produce are platinu m'iridium, gold?"coherent forms and then finish the said bodies for commercial use by myimproved rotary impact finishing process.

have found that by carrying out these steps, not only. a superiorproduct is obtained, but a product can be manufactured much moreeconomically than by means of processes now known. The refractorymetallic bodieswhich are in the arts may of any but are usuallyinsuitable shape,

the form of cylindrical discs having-a thickness not exceeding f to 4"and a diameterranging between to As it is well known, the dimensions andshapes may, however, vary according to the purposes-for be used. -Thedesired shapes or bodies are commonly used as face plates for contactsor contacts for telephony or telegraphy, for

X-ray targets, circuit controllers, rectifiers, other purposes [whichwill an for many readily suggest themselves.

My invention especially appertains to the refractory metals having anormal above, ande'specially these metals which do not acted uponmetallicbodies which are particularly de-,, bodies of tungsten, thorium,tantalum,

ignition points in. gas-engine installationsfor-magneto points,

metals can be Application medium 12, r922. Sci- 811%. 587,619.

.uraniumand alloysor mixtures of these temperature being reducedatstated times as the bodies became drawn down into with intermediatedrawing, the temperature being-likewise reduced at intervals as thecross section of the rod becomes smaller. The discs were then cut fromthe rods or else punched from the rolled plates. Que of these processesis in practice today by the General Electric Company and it is set forthat great length in Patent N 0. 1,082,933 of December 30th, 1913, toWilliam l). Coolidge, as'signor to General Electrio Company.

In order to overcome the great difficulties and to save the enormousexpense .resultin from the mechanical working of refractory metallicbodies havin a normal specific gravity above 18, and urthermore, toovercome the great difficulties of shaping these bodies into. definiteforms to make them smaller, and then either a rod by cold drawin s gannealings, or else by hot suitable as face plates for various purposesI have invented a newprocess and product which will be hereinafter setforth.- Since the bodies to be roduced are usually very small and thin,the process can be effectively carried out on a very large scale.

I have discovered a process by which dies made from y one of the metalsspecified or alloys of these metals, including tungsten, and alloys oftungsten, in which, instead of mechanically working the metal byhammering, rolling or drawing into the shape desired, I am enabled. toeliminate this long expensive proceeding. 1 have found that commercialbodies of tungsten produced by a process diflermg essentiall fromthe'special processes of the prior art in all which the forms requiredfor industrial use were produced by a special mechanical working. myprocess the metallic bodies are 'first shaped into the desired forms bypressing the metallic powder I subject the sintered body to a finishinheat is an operative temperature.

are used the tumbling 1mpact process for a considerable lengt of timeunder a constant temperature by placing the sintered shapes of tungstenwith impact balls, such as tungsten steel in a tumbling barrel, andsubjecting them during the tumbling to a heat treatment. The temperatureduring this heat treatment is but is maintained at' a below the meltingull red When not only constant temperature much of the metal. I havefound that a the recious metals and impact step may be carried out atroom temperature.

In the accompanying. drawings I have illustrated mechanisms which I havefound very suitable for use in aiding in the performance of the severalsteps of my-process.

' having a convex surface.

' sten face plate.

- and 52, as shown, to

which Fig. 4

Fig. 6 1s a cross section of a disc, one surface of which is concave andthe other convex. i I

Fig. 7 is a contact having a face plate of tungsten and a backing ofiron or steel.

Fig. 8 is a contact consisting wholly of tungsten.

Fig. 9 is a screw contact having a tung- Briefly referring to thedrawings:

The slntering furnace illustrated in Fig, 1 consists essentially of arefractory metal tube or slab of tungsten or tungsten alloy,

which has'a stationary water cooled copperelectrode 51 attached to oneend, and a .movable water cooled copper electrode 52 attached to theother end so as to allow for the expansion or contraction of the metaltube or slab 50 during the heating operation. The ends of the tungstentube 50 fit into the water cooled electrodes 51 which the main leads 53and 5a are attached, these leads being connected incircuit toatransformer' 55, conventionally shown. The entire chamber is enclosedby a. water cooled cylindrical casin which rests on supports ofinsulating material 62 and 63. The pressed up forms or shapes L tobesintered are placed upon a boat B of suitable material and are thenintroduced into the tube or point 19 meshing with a on .to'a slab throuh the opening 65. p The refractory metal s ab or tube is supported byrefractry metal rods 66 of the same material as the heating element. Theshapes to be sintered are allowed to remain in the heating element afterit has reached its maximum temperature approximately 2700 degrees C.,for about ten minutes. The current passing through the heating elementis then interrupted, the boat .is shoved into the water cooled chamber67 by means of a tungsten rod and then removed through the opening 68.The operation is carried out in an atmosphere'of hydrogen or in .1 lowpressurehydrogen vacuum. In the latter case long rubber stoppers areplaced into each end and the chamber is evacuated through a. glass tubein one of these rubber stoppers. The forms or shapes being heated byexternal means no blow holes are formed in the center and a much morecompact mass is therefore obtained.

In Fig. 2 is shown a tumbling barrel 10, the hexagonal sides being tomore eflectually throw the contacts about during its rotation, asreadily understood.

rovided with a coverll and a fixed hearing 12'on its underside throughwhich the shaft 13 extends and to which it is secured. The supportingplate 20 is provided with legs 21 and 22 of diflerent length in order'that the support may be held vat an angle The barrel 10' is to thehorizontal. On. the shaft 13 is a pulley 14 which operates a belt 15which engages a pulley 16 on a. support 17 towhich 's secured a shaft 18carrying a gear gear 19 secured to the shaft of the motor M. Therotating drum is mounted within a casing C which rests upon thesupporting plate 20, as shown. Within the casing are provided air andgas burners 30 and 40 arranged with apertures,

as shown, the burner LO'being especially arranged so that the flames mayimpinge against the lower portion of the tumbling barrel.

The products shown in Figs. to 9 are clearl illustrated, having theshapes above speci ed. a

The essential steps of my invention are as follows:

First: The production of a very fine or fine grained metallic powder ofhigh density the great fineness ofthe powder tending to produce a bodyof high specific gravity.

Second: The pressing of this dense powder into coherent bodies in thedesired shape at high pressures, thus forming the bodyinto its desiredshape and at the same time increasing the density.

Third: .The fusing or sintering of these compressed bodies in an inertor reducing atmosphere or even in vacuum or under pressure at atemperature near their melting I duce as nearly of about tile'constituents which may purposely have been introduced to draw theparticles of refractory metal together. This step further increases thedensity.

Fourth: The mechanical tumbling of the above metallic bodies either atroom temperature or at a higher temperature, which higher temperature,however, is constant but which is much below the melting point of themetal being acted upon sothat by means of this impact with hard bodies,such astungsten or vanadium steel balls',-theirjdensi ty isstill furtherincreased.

While my process is applicable to the production of bodies or shapes ofthe kind adapted for use in the arts, it is particularly applicable forthe production of dense face plates of tungsten, platinum,- iridium andtheir alloys.

In order to produce face plates of tungstem or platinum or their alloysIfirst proa chemically pure tungsten or platinum powder as possible,preferably by the reduction of the pure tungsten oxide with hydrogen, iftungsten powder is'desired, or by the ignition of ammoniumchlorplatinate if platinum is desired. These metallic powders should beas void talline structure as possible, cases I may'add a certainpercentage of crystalline powder in order to have the metal flow betterat the tablet machine. To the chemically pure metallic powders I thenadd a small percentage of a fluxing metal which alloys with: the mainconstituent at low temperatures but which is volatilized' out at thehigher temperatures and thereby has a tendencyto draw particles of themain constituents together. For tungsten, I prefer to use about 1 to 2per cent of copper, iron, 'gold or nickel.

though in some To the chemically pure tungsten powder I prefer to add 1per cent'to 1.5 per cent of chemically-pure nickel powder.and themixture of tungsten ball-milled from 10 hours to 24 hours. The ballmilling may be done in nickel contain ers usin'g balls or discs ofcoherent tungsten so that there is no contamination of impurities. Afterthis metallic powder has 'attained a weight'of about to cubic inch it isready for pressing. The pressing step is preferabl carried out on aStokestabletmachine or #0, the

shape of the disc depending upon the pur-- pose for which the'body is tobe used. As

above stated, the metal powder should be of such a'structure that itwill readily flow from the hopper and is compressed at a pressure 50tons to 100 tons per square inch. The bodies of pressed tungsten powderare placed into nickel boats and heated in hydrogen at a temperature of1000 degrees C. to 1200 degrees C. for about a quarter to as shown inFig. 1.

of crys-- and nickel powder is then 100 grams per half an hour. Thisstrength to them so that they-can be handled and still retain their sharedges. If the metal has the proper physical structureso as to produce astrong disc'this step is-not necessary.

These small bodies are then placed into the tungsten boats Bandsubjected to a heat treatment in a tungsten tube furnace such Thistreatment is referably carried out'in an atmosphereof hyimpartssuflicient drogen at a temperature of about 2700 de-- -f grees C iftungsten bodies are produced, C. to 1700 degrees C. if platinum orplatinum alloy bodies are produced. This treatment consists of acombination -sintering, volatilization and fusing action; abovetemperatures a treatment of- 5 to 10 minutes duration is sufiicient.During this treatmentthe volatile. constituents whichdistilled out. eparticles of refractory metals are draw the vmetal together are and th.and at a temperature of about 1600 degrees and at the fused together todense coherent bodies. a

fter cooling i'n'hydrogen they are removedfrom the furnace.

They are then subjected tomy impact finishing process whereb they aretumbled in a revolving barrel suc as shown in Figs.

2 and 3 with hardened I balls or impact bodies, which may be round orsharp e ged depending upon the purpose for which they are to be used.The ings which are made of Vanadium or tungsten-steel or of othertoolsteel or alloys suchwill not readily softenasstellite, etc., whichunder heat, are commonly used. The tumbling may be done at elevatedtemperatures. In the latter case the tumbling barrel may be heated bymeans otgas as shown. in Fig. 2, a metal casing C belngplaced around'thebarrel A which encloses the heat and keeps it at a uniform temperatureapproximately at 400 degrees C. The heating of the barrel may also bedone electrically. When treating substantially pure tungstendiscs,.a,dull red-heat is preferable whereas when the platinum metalsare subjected to this treatment the operation may be carried. out atroom tempera ture. During this impact finishing process the pores of thediscs are-closed, the surface of the discs are compacted and madedenser, the surface of the metallic bodies is polished and the'densityof the metallic bodies themselves is considerably'increased.

a period of from four hours to at room temperature orballs as used inbear- The tumbling is usually carried out over thirty hours dependingupon the character of'the metals 1 that are being tumbled or until themetallic bodies attainthe desired density. The turnbling may also becarried out in an inert reducing or hydrogen atmosphere.

. 'After' tumbling operation is completed the metallic bodies aretreated with weak I acids or alkalies to cleanse the surface and arethen tumbled in saw-dust after which they are ready for welding or forthe market.

The impact finishing treatment is carried I out at one temperature andnot-at a gradaful face plate of a refractory metal for uniformly heatedfrom and therefore are uniform in structure.

contacts or X ray work is that the same be of the highest densityobtainable and that it be 01? fine grain structure. Both of thesefeatures are attained through my process. Furthermore, the face-platesof tungsten or similar metals as made to-day varydecidedly in structureowing to the non-uniform heating process to which they are subjectedduring the process of manufacture whereas by my process all discs are anexternal source Thus for instance in the prior art bars of pressedtungsten are 'sintered by sending a current through the same equivalentto about 90 per cent of the fusing current in an atmosphere of hydrogen.By this means a temperature gradient is produced between the interior ofthe slug and the outsidefrom which the heat is carried by the hydrogen.This produces non-uniformity across the slug and furthermore since theends'are held at water cooled electrodes there is a decided diiferencein structure between the metal near the water-cooled electrodes and themetal near the center of the slug. All of these factors cause anon-uniformity in the structure of the discs made from rods or plates ofsuch material so that it has giventhe manufacturer of ignition systemsconsiderable trouble. Since my process subjects the-metallic bodies to amore heat treatment most of these undesirable features are eliminated.

Furthermore, any pores that may be in the metallic bodies madeaccordingto the old process remain open hich causes pitting whereas any pores inthe metallic bodies produced by my process are closed during the impacttreatment.

Another advantage of my process is also manifested in that I find thatinstead of merely making adisc I can make a complete rivet by my processsuch as shown in Fig. 8 thereby avoiding the extra operation 0 weldingthe disc on to the steel or nickel blank; This is especially desirablewhen working with tungsten or tungsten alloys or mixtures where the costofthe material I Y of which the contact is made is low enough so as topermit of this procedure. I

M process also enables me to make discs or rlvets of alloys ormixturesof the precuniform f stantially dullred heat.

ious metals and metals of the tungsten' group thereby enabling me toproduce a contact of these metals which may be substit-uted for platinumor platinum-iridium and which is equally asgood and decidedly cheaper.

Having thus described my invention, what I claim and desire'to secure byLetters Patent is: v

1. A method of forming articles of the kind described which comprisespressing fine powders of metal into a desired form, sintering the formedarticle at a high tem perature and compacting the articles at asubstantially uniform but lower temperature by an impact, tumblingaction. T

2. A method of forming articles of the kind described which comprises ametal powder containing a small quantity of a 'comparatively volatilesubstance under pressure to a desired form, volatilizing said substanceat a high temperature and compacting the article at a lower temperaturean impact, tumbling action. .3. A method of forming articles of the kinddescribed which comprises compacting a metal powder into a desired form,sintering theformed article at a high temperature and compacting saidarticle by an impact, tumbling action at .a temperature of approximately400 degrees C.

4. A method of forming .articles of the kind described whichcomprisescompacting' a metal powder containing a. small quantity-of acomparatively volatilesubstance under pressureto a desiredform,-volatilizing said substance from said article at a hightemperature and compacting said'article by an impact, tumbling action ata temperature ofapproximately 400 degrees C. in a reducing atmosphere.

5. A-me'thod of forming 'metallic articles of the kind described whichcomprises compacting a powder of metals of a density of over 18 to adesired form, metals and compacting said sintered article at asubstantially uniform lower temperature by an impact, tumbling action.

6. A method of forming metallic articles of the kind described whichcomprises comsintering sai pacting a powder of metals of a density ofover 18 with a small amount of a more vola tile metal, heating saidcompacted article to a temperature suflicient to volatilize saidmorevolatile metal, and compacting said article by an impact, tumbling.action at a sub 7. A method of forming articles of the kind describedwhich comprises compacting a powder of metals of a ensity of over 18'with a small amount of a more volatile metal. to a desired form,

and heating said articles to a temperature suflicient to volatilize saidmore volatile metal and then compact'said article by an impact, tumblingcompacting action at ture.

a substantially I uniform tempera;

8. A method of forming articles of. the

kind described which comprises compacting said article to tungstenpowder containing a small amount of nickel powder to a desired form,heating a temperature suflicientto volatilizesaid nickel and compactingsaidarticle at a lower temperature by an' impacg tumbling action.

9. An article pf manufacture comprising a body of tungsten of highdensity which is free from a fibrous structure, the surface of which hasbeen still further densified by an impact, tumbling action. Y

10. An article of manufacture comprising a refractory metal of highspecific gravity,- the density of the surface of which is increased overthat on the inside of the body by an impact, tumbling action at atempera- 20 ture approximating a dull red heat.

11. An article of manufacture comprising a contact oftungsten of highdensity which is free from a fibrousstructure, the surface of whichbeing denser than'theinside, the said surface being formed by an impact,tumbling action.

In witness whereof I have hereunto set myhand at the borough'ofManhattan, city and State of New York, this 6th day of 30 June, 1922.

' one A. SE.

